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Add filter examples for Cancel-Lock/-Key.

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This is a possible implementation of Cancel-Lock
and Cancel-Key. cleanfeed.local will check for
a matching Cancel-Key before accepting a cancel,
filter_nnrpd.pl will add Cancel-Locks to all
postings (and a matching Cancel-Key to cancel
messages).

See also
http://th-h.de/blog/archives/1473-INN-Cancel-Lock-und-Cancel-Key.html

Signed-off-by: Thomas Hochstein <thh@inter.net>
This commit is contained in:
Thomas Hochstein 2011-12-18 01:51:35 +01:00
parent d4dd9a5895
commit 8faa6b210c
2 changed files with 155 additions and 0 deletions
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102
filter/cleanfeed.local Normal file
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# vim: set syntax=perl ts=4 ai si:
use MIME::Base64();
use Digest::SHA1();
use Digest::HMAC_SHA1();
#
# local_filter_cancel
#
sub local_filter_cancel {
unless($hdr{Control} =~ m/^cancel\s+(<[^>]+>)/i) {
return "Cancel with broken target ID";
}
return verify_cancel(\%hdr, $1, 'Cancel');
}
sub local_filter_after_emp {
if (exists( $hdr{'Supersedes'} )) {
#return verify_cancel(\%hdr, $hdr{'Supersedes'}, 'Supersedes');
# verify_cancel is called, but not returned, so the
# posting is unconditionally accepted
# verify_cancel calls INN:cancel() if verification suceeds
verify_cancel(\%hdr, $hdr{'Supersedes'}, 'Supersedes');
}
return undef;
}
sub verify_cancel($$$) {
my $r_hdr = shift || die;
my $target = shift;
my $descr = shift;
my $headers = INN::head($target) || return "$descr of non-existing ID $target";
my %headers;
for my $line(split(/\s*\n/, $headers)) {
if ($line =~ m/^([[:alnum:]-]+):\s+(.*)/) {
$headers{$1} = $2;
}
}
my $lock = $headers{'Cancel-Lock'};
if (defined($lock)) {
my $key = $r_hdr->{'Cancel-Key'} || return "$descr of $target without Cancel-Key";
#return verify_cancel_key($key, $lock, ' target=' . $target);
return verify_cancel_key($key, $lock, $target);
} else {
# -thh
# no cancel-lock: go ahead and cancel anyway!
INN::cancel($target);
}
return undef;
}
sub verify_cancel_key($$$) {
my $cancel_key = shift;
my $cancel_lock = shift;
my $msg = shift;
$msg = '' unless(defined($msg));
# -thh
my $target = $msg;
$msg = ' target=' . $msg;
my %lock;
for my $l(split(/\s+/, $cancel_lock)) {
next unless($l =~ m/^(sha1|md5):(\S+)/);
$lock{$2} = $1;
}
for my $k(split(/\s+/, $cancel_key)) {
unless($k =~ m/^(sha1|md5):(\S+)/) {
INN::syslog('notice', "Invalid Cancel-Key syntax '$k'.$msg");
next;
}
my $key;
if ($1 eq 'sha1') {
$key = Digest::SHA1::sha1($2); }
elsif ($1 eq 'md5') {
$key = Digest::MD5::md5($2);
}
$key = MIME::Base64::encode_base64($key, '');
if (exists($lock{$key})) {
# INN::syslog('notice', "Valid Cancel-Key $key found.$msg");
# -thh
# article is canceled now
INN::cancel($target) if ($target);
return undef;
}
}
INN::syslog('notice',
"No Cancel-Key[$cancel_key] matches Cancel-Lock[$cancel_lock]$msg"
);
return "No Cancel-Key matches Cancel-Lock.$msg";
}
1;